Rotary mixer

ABSTRACT

A manually actuatable rotary mixer having a surprisingly simple and inexpensive construction is disclosed. The device includes a rotary mixing assembly driven by a reciprocating spiral shaft received within a hollow mixer shaft from which the mixing elements radially extend. The mixer shaft is mounted fast on a bearing member having a corresponding internal spiral surface and vertically supported on a retainer plate. The retainer plate is disposed between the mixing container and a cover member through which the actuating shaft extends and means are provided on the cover member for operatively threadedly securing it to the mixing container and for pressing the retainer plate into sealing engagement with the lip of the mixing container when the cover member is tightened thereon. A compression coil spring between the retainer plate and the cover member is effective to return the actuating shaft to its upper position after manual depression thereof, thereby to effect a rapid alternate clockwise and counterclockwise rotation of the mixing elements within the container.

United States Patent 1 Blasnik 1 July 10, 1973 Primary Examiner-Robert W. Jenkins Attorney Maxwell James and Harold James [57] ABSTRACT A manually actuatable rotary mixer having a surpris ingly simple and inexpensive construction is disclosed. The device includes a rotary mixing assembly driven by a reciprocating spiral shaft received within a hollow mixer shaft from which the mixing elements radially extend. The mixer shaft is mounted fast on a bearing member having a corresponding internal spiral surface and vertically supported on a retainer plate. The retainer plate is disposed between the mixing container and a cover member through which the actuating shaft extends and means are provided on the cover member for operatively threadedly securing it to the mixing container and for pressing the retainer plate into sealing engagement with the lip of the mixing container when the cover member is tightened thereon.

A compression coil spring between the retainer plate and the cover member is effective to return the actuating shaft to its upper position after manual depression thereof, thereby to effect a rapid alternate clockwise and counterclockwise rotation of the mixing elements within the container.

18 Claims, 8 Drawing Figures 3 -szA 31 4 440 20 T 2A 5 mmmm 1 man SHEEI 3 0f 3 FIG. 6

ROTARY MIXER This invention relates to rotary mixers and more particularly to a manually actuatable rotary mixer or blender of the type used in food preparation.

As the art of cooking has advanced in recent years, the use of food mixing and blending mechanisms has steadily increased. Today a rotary mixer or blender is regarded as a necessary cooking aid not only for the professional cook but also for home use. The variety of food mixing or blending operations called for in todays popular home cooking recipes requires mixers or blenders having a variety of speeds and operating characteristics.

While the modern electrically operated high speed rotary mixer or blender is quite versatile, there are many blending and mixing operations which are not satisfactorily performed by such mechanisms. These include operations in which the contents must be relatively slowly agitated to a subtly defined consistency and/or in which the consistency is preferably primarily controlled by the feel of the operator. Moreover, in some cases it is desirable to continuously vary the speed of mixing in response to such feel. Indeed, many serious cooks consider food preparation an art in which high speed electric mixers or blenders are laboratory type instruments unsuitable for food preparation because they are relatively unresponsive to the artistry of the cook.

However, for most mixing operations manual agitation with a hand held utensil may be equally unsuitable as a result of the time and manual effort which is generally required. As a result, manually actuatable rotary food mixers are still quite popular among many cooks. These devices represent a compromise between the undesirable insensitivity and lack of control of the high speed electric blender actuated by the flick of the switch and the equally undesirable time consumption and fatigue involved in the tedious process of manual mixing with a hand held utensil.

Various styles and types of manually actuatable mixers have been available for many years. Mechanisms of this type generally comprise a mixing element assembly actuated by a rotatable or reciprocating actuator and adapted to be hand held over a container with the mixing assembly extending downwardly into the contents to be mixed. These devices, however, have many drawbacks, perhaps the most important of which are the problems of slippage and fatigue. It is often difficult to stabilize the mixer unit over the container particularly when the food products being mixed are viscous. As a result, substantial effort must be expended to maintain the container and the mixing unit in operative relationship for effective mixing action.

A second disadvantage of these prior art devices is that they are not designed for use with containers of any particular size, shape or depth. While this provides versatility, it often contributes significantly to the problems of slippage and fatigue.

Moreover, devices of this character are generally limited by the physical capabilities of the user to very low speeds. Where high speed capability has been attempted, the resulting mechanisms have been found to require unduly large amounts of manual pressure on the actuating means to overcome the high torque ratio with a resulting loss of adequate speed control and an increase in slippage and fatigue.

Finally, commercially available devices of this type, while substantially less expensive than electric blenders, are generally unduly complex, expensive to manufacture and prone to failure.

It is a primary object of the present invention to provide a food mixing device of the manually actuatable type which eliminates substantially all of the problems of prior art mixers of this type.

It is yet another object of the present invention to design a rotary mixer of the type described which is adapted for releasable sealing attachment to a mixing container.

It is yet another object of the present invention to provide a manually actuatable rotary mixer including an improved reciprocating drive mechanism which provides effective rotary mixing action at high speeds approaching that of electric mixers with a minimum of fatigue.

It is still another object of the present invention to design a rotary mixer of the type described which is easy to operate inexpensive to manufacture and assemble, and provides a particularly effective versatile mixing action for a variety of food products.

To these ends, the present invention comprises a manually actuatable rotary mixer having a simple and inexpensive construction yet being surprisingly effective for its intended purpose. Briefly, that construction comprises a cover member and a mixing container releasably secured to one another. A retainer plate is releasably secured to the cover member and means are provided for bringing that retainer plate into sealing engagement with the lip of the mixing container when the device is assembled.

A rotary mixing means in the form of a hollow shaft having radially extending mixing elements is vertically supported on the retainer plate and extends substantially fully into the mixing container. The actuating member comprises a shaft extending through the cover member and having a knob or handle on its outwardly extending end. The other end of the actuating shaft is externally threaded in a spiral configuration and is received within the hollow mixing shaft. That hollow shaft is provided with an internal low friction bearing member internally threaded for driving engagement with the actuating shaft. The actuating shaft is spring biased to an upper position by means of a concentric coil spring compressed between the retainer plate and a washer mounted concentrically on the actuating shaft and forced upwardly into engagement with a radial projection thereon.

The device is operated by a simple reciprocating motion of the actuator shaft. Thus, when the shaft is pushed downwardly against the bias of the compression spring, the threaded engagement between the spiral threads on the actuating shaft and the internally threaded bearing member is effective to convert the axial movement of the actuating shaft into a rotary movement of the hollow mixer shaft thereby to rotate the mixing elements within the container. The downward end of the stroke is defined by the engagement of a shoulder of the actuating knob with the cover member. Upon release of the pressure on the knob, the compression spring is effective to force the actuating shaft upwardly to its initial position thereby to rotate the hollow mixing shaft and the radially extending mixing elements in the reverse direction. The upper end of the stroke is defined by the engagement of the spring biased washer with the underside of the cover member.

In a preferred embodiment of the invention, the mixer shaft extends through an aperture on the retainer plate and is supported in depending relation therefrom by a radially projecting flange or lip on the bearing member engaging the upper surface of the retainer plate. The bearing flange is maintained in substantially sealing relationship with the retainer plate during the operation of the actuating shaft by the action of the aforementioned compression spring which engages a washer seated on that flange. As a result, the lower or mixing chamber is sealed by the retainer plate and food particles are prevented from entering the upper chamber defined between the retainer plate and the cover member.

The retainer plate is preferably detachable from the cover member and may be moved downwardly on the actuating shaft for cleaning but the actuating shaft is preferably deformed at its lower end to prevent the assembly from completely detaching when removed for cleaning.

To the accomplishment of the above, and to such other objects as may hereinafter appear, the present invention relates to a manually actuatable rotary mixer as defined in the appended claims and as described herein with reference to the accompanying drawings, in which:

FIG. I is a perspective view of the rotary mixer of the present invention;

FIG. 2 is a cross sectional view of the rotary mixer of FIG. 1 taken generally along the line 2-2 of FIG. 1;

FIG. 2A is an enlarged fragmentary cross sectional view taken along the line 2A-2A of FIG. 2;

FIG. 3 is an enlarged fragmentary side elevational view partly in section of the threaded bearing and spiral shaft assembly of the rotary mixer of FIG. 1;

FIG. 4 is a cross sectional view taken along the line 44 of FIG. 3;

FIG. 5 is an enlarged cross sectional view of the spiral bearing of FIG. 3;

FIG. 6 is a cross sectional view taken along the line 6-6 of FIG. 2; and

FIG. 7 is a cross sectional view of the rotary mixer assembly taken along the line 77 of FIG. 2.

The rotary mixer of the present invention is best illustrated in FIGS. 1 and 2 and comprises a mixing container or jar generally designated 10, a cover member generally designated 12 operatively secured to container 10, a rotary mixer assembly generally designated 14 received within the container and a reciprocating drive mechanism generally designated 16 operatively connected to the rotary mixing assembly 14 and slidably received within cover member 12. As best shown in FIG. 2, container 10 is shaped in the form of a conventional jar having a bottom 10a and a cylindrical slightly outwardly bowed side wall 10b and is provided with a recessed lip 17 externally threaded at 18 for lockingly receiving a conventional threaded cap or cover. Cover member 12 is generally shaped in the form of an angularly truncated inverted funnel l9 having a top wall 19a and a generally cylindrical base portion 20 and is provided internally on base portion 20 at its lower edge with threads 22 adapted to operatively lockingly threadedly engage the corresponding threads 18 on the external surface of the lip 17 of the container or jar 10. Accordingly, in the assembled condition, the cover member 12 is threadedly secured to the jar 10,

its lower cylindrical base portion 20 being substantially coterminous with the outer cylindrical side wall 10b of container 10 as show n in FIG. 1.

A retainer plate generally designated 24 is disposed between the cover member 12 and the container 10, thereby to separate the resulting enclosure into an upper chamber 26 and a lower mixing chamber 28. Retainer plate 24 is formed with a downwardly projecting central portion 30 and a peripheral flange 32. As best shown in FIG. 6, portion 30 is formed in the shape of a truncated cone 31 having four radially projecting fingers 34 and is provided with a central aperture 33. As again best shown in FIG. 6, the retainer flange 32 has an outer diameter approximately equal to the outer diameter of container rim l7 and is provided with a plurality of radially projecting tabs 38 (here shown as four) extending substantially to the inner surface of the cylindrical base portion 20 of cover member 12. In addition, retainer plate 24 is provided at its undersurface with a downwardly extending circular rib 40 having a diameter slightly less than that of the inner surface of container lip 17, whereby the retainer plate 24 may be centered on the lip 17 and when forced downwardly thereon may be brought into sealing engagement therewith.

As best shown in FIG. 2A, cover member 12 is provided internally on its cylindrical base portion with four radially inwardly extending vertical ribs 42 (see also FIG. 6). Centered below each vertical rib 42 and vertically spaced therefrom is a generallyL-shaped rib 44 comprising a horizontally extending support portion 44a and a stop portion 44b vertically extending upwardly from support portion 44a. The other end of sup: port portion 44a is open and defines together with rib 42 a slot 46 adapted to receive tab 38 (see FIG. 2A). Accordingly, the retainer plate 24 may be operatively secured to the cover member 12 merely by inserting that retainer plate upwardly against the vertical ribs 42 with the tabs 38 spaced between consecutive L-shaped ribs 44 and thence gripping the fingers 34 and turning the cover member a quarter of a turn counterclockwise (as viewed in FIG. 6) to slide the tabs 38 into operative engagement with the vertical stop portion 44b of the L-shaped rib 44, whereupon the tabs 40 of retainer plate 24 are vertically supported on horizontal support ribs 44a, respectively. When so supported, the retainer flange is slightly vertically spaced below vertical ribs 42, the slot 46 being slightly larger than the thickness of tabs 38. However, upon screwing cover member 12 onto container 10, the under surface of flange 32 engages the top edge of rim 17 of the container, the circular rib 40 engages the internal vertical wall of rim 17, and as the cover member is tightened on container 10, the tabs 38 are lifted off support ribs 44a and the flange 32 engages vertical ribs 42 at its upper surface, those ribs being effective to press the flange 32 and rib 40 into good sealing engagement with the rim 17 of the container. 4

Referring again to FIG. 2, the operative rotary mixer assembly comprises a hollow shaft 50 having an open top end received within the central aperture 33 in retainer plate 24. The bottom end of shaft 50 is closed by end wall 52. The shaft 50 is provided with a plurality of mixing elements, here shown as three mixing blades 54, formed integral therewith and extending radially outwardly thereof in equally spaced relationship.

Mixing blades 54 are here shown with a particular contour adapted to provide a desirable smooth and uniform mixing action within the lower mixing chamber 28. As illustrated the blades are generally U-shaped and include a generally narrow inner arm 54a radially projecting from shaft 50 along substantially its entire operative length, a base portion radially extending from the bottom end of shaft 50 with its lower edge coterminous with end wall 52 and slightly spaced above the bottom wall a of the container, and an outer arm 54c extending upwardly from base portion 54b approximately half way to the retainer plate 24. The opposing edges of arms 54a and 540 are gracefully flared downwardly toward each other to define a curved crevice 56 at the upper edge of base portion 54b. The outer edge of the arm 540 extends virtually to the base of the side wall 10b of the container and is preferably formed with a bevelled surface 58 at its intersection with the lower edge of the base 54b.

The thus contoured blade provides effective uniform rotary mixing action for most food products. The blades 54 and shaft 50 may be molded in one piece of a light weight durable plastic, thereby to reduce the necessary drive torque for high speed rotary action. Upon rotation of the shaft 50 the blades 54 engage and move through the food particles in the container driving them radially outwardly against the side wall 10b of the container and upwardly against the retainer plate 24, the particles thence falling back onto the arcuate crevice edge 56 of the blades for thorough and uniform mixing action.

The mixing assembly 14 is supported on retainer plate 24 by means of a bearing member generally designated 60. As best shown in FIGS. 4 and 5, bearing member 60 comprises a hollow cylinder 62 having a flange 64 projecting radially outwardly at its upper end. The cylinder 62 is generally circular with an outer diameter approximately equal to the inner diameter of hollow shaft 50 and is provided with a plurality of radially outwardly projecting vertical splines 66. Those splines are adapted to be received within corresponding vertical keyways 68 formed on the internal surface of hollow shaft 50 (see FIG. 4) at its upper end and extending downwardly a distance at least equal to the length of splines 66.

As best shown in FIG. 3, the lower end of the bearing member 60 is inserted into the open upper end of the hollow shaft 50, the splines 66 being received within keyways 68, and pressed downwardly until the flange 64 engages the upper end of shaft 50. The parts are dimensioned for press-fit engagement so that shaft 50 is vertically suspended and rotatably keyed to bearing 60. During assembly this press-fit engagement is effected after shaft 50 is received through central aperture 33 in retainer plate 24. Accordingly, in the assembled condition retainer plate 24 is captured on the upper end of shaft 50 between the overhanging bearing flange 64 and the upper end of the blade arms 54. Upon securing the retainer plate 24 to the cover member 12 as described above, the bearing flange 64 engages the upper surface of the plate 24 at the edge of aperture 33 (see FIG. 3) and thus the bearing member 60 and mixer assembly 14 are vertically supported on and suspended from the retainer plate.

The depth of container 10 is such that in the assembled condition the blade assembly extends downwardly into the container to a depth only slightly spaced from the lower wall 10a of the container. In order to prevent the lower edges of the blades 54 from engaging the bottom of the container, a small downwardly extending projection 70 may be provided on the end wall 52 of the hollow shaft 50.

The hollow cylinder 62 of bearing member 60 is counterbored at its upper endat 72 and is internally threaded at 74 to threadedly receive the threaded lower end 76 of an actuating shaft 78. The other end of shaft 78 extends through an aperture 80 in the top wall 19a of the cover member 12 and is provided with a knob generally designated 82. As best shown in FIG. 2, knob 82 comprises a generally horizontal (rounded) portion 84 and a downwardly projecting stud 86 having a bore 88 receiving the upper end of shaft 78 in pressflt relationship. Accordingly, as shaft 78 is moved downwardly by manual pressure on handle 82 in the direction of arrow 90 the externally threaded portion 76 on the lower end of the shaft operatively drivingly engages the internally threaded portion 74 of bearing 60 to rapidly rotate the bearing in a counterclockwise direction as viewed in FIG. 6.

As best shown in FIGS. 3 and 4, the threaded portion 76 of shaft 78 is preferably defined by a quadrate spiral. As best shown in FIG. 4, the spiral shaft portion 76 is generally square in cross section, its side surfaces 76a being slightly arcuately bowed inwardly and that cross section being rotated continuously for approximately two complete revolutions along the full length of the threaded section 76 to form a spiral. The threaded bearing section 74 has a corresponding spiral inner surface and accordingly the bearing 60 makes approximately two complete revolutions counterclockwise for a full downward stroke of shaft 78.

The lower end of that stroke is defined by the engagement of the stud 86 on handle 82 with the upper wall 190 of the cover member 12 as illustrated in the broken line position of FIG. 2. As the spiral portion of the shaft 76 moves downwardly through bearing 60 it is received within the hollow shaft 50, the stroke of actuating shaft 78 preferably being terminated with the lower end of the spiral portion 76 spaced from the lower wall 52 of the hollow shaft 50.

Spaced slightly above the upper end of the spiral portion 76 of shaft 78 within upper chamber 26 is a pin 92 extending through the shaft 78 and radially outwardly thereof. That pin 92 is disposed between a pair of washers 94 and 96, respectively, mounted concentrically on shaft 78 below the upper wall 19a of cover member 12. A lower washer 98 is disposed concentrically on the spiral portion 76 of shaft 78 directly above the flange 64 of bearing 60. A compression coil spring is compressed between the washers 96 and 98 thereby to urge the pin 92 and thus the shaft 78 upwardly to the solid line position illustrated in FIG. 2, washer 94 engaging the underside of the upper wall 19a of cover member 12. Accordingly, as the shaft 78 is moved downwardly by pressure on handle 82 in the direction of arrow 90, pin 92 and washer 96 are effective to compress coil spring 100, that coil spring being effective to return the shaft to the upper solid line position of FIG. 2 upon releasing the pressure on the handle 82 thereby to automatically rotate the mixing assembly 14 in the opposite (clockwise) direction (as viewed in FIG. 6) to complete one reciprocating cycle of the shaft 78.

In addition to automatically providing a return stroke, coil spring 100 is also effective to maintain the bearing flange 64 firmly engaged against the upper surface of retainer plate 24 thereby to maintain the lower mixing chamber 28 substantially sealed. At the same time, the flange 64 must rotate first in one direction and then in the other on the upper surface of retainer 24. Accordingly, that bearing member 60 is preferably made of a low friction synthetic material which provides a minimum of frictional resistance not only between the flange 64 and the retainer plate 24 but also between the spiral thread 76 on shaft 78 and its corresponding internally threaded surface 74. As a result, surprisingly little resistance to the downward stroke of shaft 78 is encountered and even a simple pressure engagement on the horizontal portion 84 of handle 82 by the palm of the hand is effective to prevent the shaft 78 itself from rotating, thereby to positively rotatably drive the mixing assembly. Moreover, the spring 100 need be only moderately stiff in order to rapidly and effectively return the shaft 78 to is upper solid line position as illustrated in FIG. 2.

In order to prevent the mixer assembly 14 from detaching from the shaft 78 when it is removed for cleaning (as hereinafter described), the lower end of that shaft is deformed at 102 so as to act as a stop member not threadedly received through bearing member 60.

The rotary mixer described above is surprisingly inexpensive to manufacture and assemble. Thus, in addition to the mixing assembly 14, the retainer plate 24, the cover member 12 and the knob 82 may all be molded in a convenient assembly line process from a relatively inexpensive but durable plastic. Moreover, the parts need not be manufactured to any particularly close tolerance since the sealing function of the retainer plate both at the rim of the container and at the central aperture 33 thereof is accomplished by positive pressure of the vertical ribs 42 and the compression spring 100 respectively. Thus, the opening or slot 46 between the vertical ribs 42 and the horizontal support ribs 44a on the cover member 12 (see FIG. 2A) need only be Iarg'er'than the thickness of tabs 38 on the retainer plate, those vertical ribs 42 automatically pressing the retainer flange 32 into sealing engagement with the container rim 17 upon tightening of the cover member. Likewise, the central aperture 33 in retainer plate 24 may be substantially larger in diameter than the outer diameter of shaft 50 provided it is smaller than the diameter of the sealing flange 64 on bearing member 60.

The mixer is conveniently assembled as follows: The bearing member 60 is received on the upper ends of shaft 78 and screwed downwardly onto the spiral portion 76 thereof. The upper end of the shaft 50 is inserted through the aperture 33 in retainer plate 24 and then the bearing member 60 is inserted into the hollow at the upper end of shaft 50 and press-fit therein whereby the retainer plate 24 is captured between the flange 64 and the upper edges of blade arms 54a. Next, washer 98, spring 100 and washer 92 are mounted concentrically on shaft 78, spring 100 is slightly compressed by pressure on washer 96 and pin 92 is inserted through the shaft above washer 96. Washer 94 and the cover member 12 are then mounted on shaft 78 in the operative relationship illustrated and the knob 82 is thereafter press fit on the upper end of the shaft. The resulting structure is retained in one piece, the parts all being retained on the drive shaft 78 between the deformed lower end 102 and the knob 82. Accordingly,

the user need not be burdened with assembling and disassembling the device each time it is used.

In operation the food contents are merely placed in the mixing jar 10, the retainer plate 24 is screwed into operative position on the cover member 12 by turning a quarter of a turn as described hereinbefore and the cover member is screwed onto the jar to the position illustrated in FIG. 2. The speed of mixing is controlled by the rate of depression of the reciprocating drive shaft. For normal cleaning, the user need not detach the retainer plate 24 from the cover member 12 but merely cleans the underside of the retainer plate. An occasional cleaning of the underside of the bearing flange 64 and the upper surface of the retainer flange 32 may be accomplished simply by unscrewing the retainer plate from the cover member and moving it downwardly against the upper edges of the blade arms 54a. The mixed contents may be stored in the same container 10 by securing a conventional screw-on cover thereto, which cover may be provided with the mixing unit.

The low cost of manufacture and surprising effectiveness of the rotary mixer herein described offers the consumer an attractive and useful food preparation aid at a cost far below that of devices of comparable effectiveness.

While only a single embodiment of the present invention has herein been specifically described, it will be appreciated that many variations may be made therein without departing from the scope of the invention, as defined in the following claims.

I claim:

1. A manually actuatable rotary mixer comprising a mixing container adapted to receive the contents to be mixed, a cover member, means on said cover member for removably securing it to said container, separate retainer means disposed between said container and said cover member and defining with said container and cover member a lower mixing chamber and an upper chamber, rotary mixing means vertically supported on said retainer means and extending into said container, manually actuatable reciprocating drive means operatively connected to said rotary mixing means, slidably received in said cover member for movement between first and second positions and effective in response to sliding movement thereof to rotatably drive said mixing means within said mixing chamber, and means on said cover member engaging said retainer means and effective to produce sealing engagement of said retainer means with said container when said cover member is secured to said container.

2. The rotary mixer of claim 1, wherein said rotary mixing means comprises a hollow shaft extending into said container and having a plurality of radially extending mixing elements, wherein said cover member is provided with an aperture and wherein said drive means comprises an externally threaded drive shaft having one end extending through said aperture in said cover member and its other end received within said hollow shaft and means on said hollow shaft threadedly engaging said drive shaft, whereby when said threaded drive shaft is moved downwardly into said hollow shaft said mixing means is rotated in a given direction.

3. The rotary mixer of claim 2, wherein said drive shaft engaging means comprises bearing means having a main body portion received within said hollow mixing shaft at one end thereof and a flange engaging said one end of said hollow shaft and extending laterally therebeyond, said retainer means comprising a retainer plate having an aperture receiving said hollow mixing shaft and vertically supporting said mixing means by engagement with said bearing flange.

4. The rotary mixer of claim 3, wherein said hollow shaft is press fit onto said cylindrical bearing portion, and means keying said bearing member to said hollow shaft for rotary movement together.

5. The rotary mixer of claim 3, wherein said drive shaft further comprises a deformed portion at the lower end thereof below said bearing means thereby to prevent said lower end of said drive shaft from moving through said bearing means.

6. The rotary mixer of claim 2, wherein said externally threaded drive shaft comprises a quadrate spiral.

7. The rotary mixer of claim 6, wherein said drive shaft engaging means comprises bearing means having a main body portion received within said hollow mixing shaft at one end thereof and a flange engaging said one end of said hollow shaft and extending laterally therebeyond, said retainer means comprising a retainer plate having an aperture receiving said hollow mixing shaft and vertically supporting said mixing means by engagement with said bearing flange.

8. The rotary mixer of claim 1, wherein said container has a rim having an upper edge and an inner wall and wherein said retainer means comprises a flange, and means on said cover member effective when said cover member is secured to said container to operatively engage said retainer flange and press same into sealing engagement with the upper edge of said container rim.

9. The rotary mixer of claim 8, wherein said retainer flange further comprises a vertically depending rib extending into said container and adapted to sealingly engage said inner wall of said container rim when said retainer flange is pressed into sealing engagement with the upper edge of said container rim.

10. The rotary mixer of claim 9, wherein said cover member comprises a cylindrical side wall and wherein said flange pressing means comprises a plurality of vertical ribs radially inwardly projecting from said cylin' drical side wall of said cover member.

11. The rotary mixer of claim 8, wherein said rotary mixing means comprises a hollow shaft extending into said container and having a plurality of radially extending mixing elements, wherein said cover member is provided with an aperture and wherein said drive means comprises an externally threaded drive shaft having one end extending through said aperture in said cover member and its other end received within said hollow shaft and means on said hollow shaft threadedly engaging said drive shaft, whereby when said threaded drive shaft is moved downwardly into said hollow shaft said mixing means is rotated in a given direction.

12. The rotary mixer of claim 11, wherein said drive shaft engaging means comprises bearing means having a main body portion received within said hollow mixing shaft at one end thereof and a flange engaging said one end of said hollow shaft and extending laterally therebeyond, said retainer means comprising a retainer plate having an aperture receiving said hollow mixing shaft and vertically supporting said mixing means by engagement with said bearing flange.

13. The rotary mixer of claim 12, wherein said retainer flange further comprises a vertically depending rib extending into said container and adapted to sealingly engage said inner wall of said container rim when said retainer flange is pressed into sealing engagement with the upper edge of said container rim.

14. The rotary mixer of claim 8, further comprising means on said cover member vertically supporting said retainer flange in a position spaced below said flange pressing means whereby upon securing said cover member to said container, said retainer means is lifted from said supporting means by said container rim and pressed into sealing engagement with said container rim by said flange pressing means.

15. The rotary mixer of claim 14, wherein said retainer flange further comprises a vertically depending rib extending into said container and adapted to sealingly engage said inner wall of said container rim when said retainer flange is pressed into sealing engagement with the upper edge of said container rim.

16. The rotary mixer of claim 15, wherein said cover member comprises a cylindrical side wall and wherein said flange pressing means comprises a plurality of vertical ribs radially inwardly projecting from said cylindrical side wall of said cover member.

17. The rotary mixer of claim 14, wherein said rotary mixing means comprises a hollow shaft extending into said container and having a plurality of radially extending mixing elements, wherein said cover member is provided with an aperture and wherein said drive means comprises an externally threaded drive shaft having one end extending through said aperture in said cover member and its other end received within said hollow shaft and means on said hollow shaft threadedly engaging said drive shaft, whereby when said threaded drive shaft is moved downwardly into said hollow shaft said mixing means is rotated in a given direction.

18. The rotary mixer of claim 17, wherein said drive shaft engaging means comprises bearing means having a main body portion received within said hollow mixing shaft at one end thereof and a flange engaging said one end of said hollow shaft and extending laterally therebeyond, said retainer means comprising a retainer plate having an aperture receiving said hollow mixing shaft and vertically supporting said mixing means by engagement with said bearing flange. 

1. A manually actuatable rotary mixer comprising a mixing container adapted to receive the contents to be mixed, a cover member, means on said cover member for removably securing it to said container, separate retainer means disposed between said container and said cover member and defining with said container and cover member a lower mixing chamber and an upper chamber, rotary mixing means vertically supported on said retainer means and extending into said container, manually actuatable reciprocating drive means operatively connected to said rotary mixing means, slidably received in said cover member for movement between first and second positions and effective in response to sliding movement thereof to rotatably drive said mixing means within said mixing chamber, and means on said cover member engaging said retainer means and effective to produce sealing engagement of said retainer means with said container when said cover member is secured to said container.
 2. The rotary mixer of claim 1, wherein said rotary mixing means comprises a hollow shaft extending into said container and having a plurality of radially extending mixing elements, wherein said cover member is provided with an aperture and wherein said drive means comprises an externally threaded drive shaft having one end extending through said aperture in said cover member and its other end received within said hollow shaft and means on said hollow shaft threadedly engaging said drive shaft, whereby when said threaded drive shaft is moved downwardly into said hollow shaft said mixing means is rotated in a given direction.
 3. The rotary mixer of claim 2, wherein said drive shaft engaging means comprises bearing means having a main body portion received within said hollow mixing shaft at one end thereof and a flange engaging said one end of said hollow shaft and extending laterally therebeyond, said retainer means comprising a retainer plate having an aperture receiving said hollow mixing shaft and vertically supporting said mixing means by engagement with said bearing flange.
 4. The rotary mixer of claim 3, wherein said hollow shaft is press fit onto said cylindrical bearing portion, and means keying said bearing member to said hollow shaft for rotary movement together.
 5. The rotary mixer of claim 3, wherein said drive shaft further comprises a deformed portion at the lower end thereof below said bearing means thereby to prevent said lower end of said drive shaft from moving through said bearing means.
 6. The rotary mixer of claim 2, wherein said externally threaded drive shaft comprises a quadrate spiral.
 7. The rotary mixer of claim 6, wherein said drive shaft engaging means comprises bearing means having a main body portion received within said hollow mixing shaft at one end thereof and a flange engaging said one end of said hollow shaft and extending laterally therebeyond, said retainer means comprising a retainer plate having an aperture receiving said hollow mixing shaft and vertically supporting said mixing means by engagement with said bearing flange.
 8. The rotary mixer of claim 1, wherein said container has a rim having an upper edge and an inner wall and wherein said retainer means comprises a flange, and means on said cover member effective when said cover member is secured to said container to operatively engage said retainer flange and press same into sealing engagement with the upper edge of said container rim.
 9. The rotary mixer of claim 8, wherein said retainer flange further comprises a vertically depending rib extending into said container and adapted to sealingly engage said inner wall of said container rim when said retainer flange is pressed into sealing engagement with the upper edge of said container rim.
 10. The rotary mixer of claim 9, wherein said cover member comprises a cylindrical side wall and wherein said flange pressing means comprises a plurality of vertical ribs radially inwardly projecting from said cylindrical side wall of said cover member.
 11. The rotary mixer of claim 8, wherein said rotary mixing means comprises a hollow shaft extending into said container and having a plurality of radially extending mixing elements, wherein said cover member is provided with an aperture and wherein said drive means comprises an externally threaded drive shaft having one end extending through said aperture in said cover member and its other end received within said hollow shaft and means on said hollow shaft threadedly engaging said drive shaft, whereby when said threaded drive shaft is moved downwardly into said hollow shaft said mixing means is rotated in a given direction.
 12. The rotary mixer of claim 11, whereIn said drive shaft engaging means comprises bearing means having a main body portion received within said hollow mixing shaft at one end thereof and a flange engaging said one end of said hollow shaft and extending laterally therebeyond, said retainer means comprising a retainer plate having an aperture receiving said hollow mixing shaft and vertically supporting said mixing means by engagement with said bearing flange.
 13. The rotary mixer of claim 12, wherein said retainer flange further comprises a vertically depending rib extending into said container and adapted to sealingly engage said inner wall of said container rim when said retainer flange is pressed into sealing engagement with the upper edge of said container rim.
 14. The rotary mixer of claim 8, further comprising means on said cover member vertically supporting said retainer flange in a position spaced below said flange pressing means whereby upon securing said cover member to said container, said retainer means is lifted from said supporting means by said container rim and pressed into sealing engagement with said container rim by said flange pressing means.
 15. The rotary mixer of claim 14, wherein said retainer flange further comprises a vertically depending rib extending into said container and adapted to sealingly engage said inner wall of said container rim when said retainer flange is pressed into sealing engagement with the upper edge of said container rim.
 16. The rotary mixer of claim 15, wherein said cover member comprises a cylindrical side wall and wherein said flange pressing means comprises a plurality of vertical ribs radially inwardly projecting from said cylindrical side wall of said cover member.
 17. The rotary mixer of claim 14, wherein said rotary mixing means comprises a hollow shaft extending into said container and having a plurality of radially extending mixing elements, wherein said cover member is provided with an aperture and wherein said drive means comprises an externally threaded drive shaft having one end extending through said aperture in said cover member and its other end received within said hollow shaft and means on said hollow shaft threadedly engaging said drive shaft, whereby when said threaded drive shaft is moved downwardly into said hollow shaft said mixing means is rotated in a given direction.
 18. The rotary mixer of claim 17, wherein said drive shaft engaging means comprises bearing means having a main body portion received within said hollow mixing shaft at one end thereof and a flange engaging said one end of said hollow shaft and extending laterally therebeyond, said retainer means comprising a retainer plate having an aperture receiving said hollow mixing shaft and vertically supporting said mixing means by engagement with said bearing flange. 